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Ms Margaret Lagono S E C ® R August 1, 2005 f Page 5 t During the second quarter 2005 groundwater flow was to the southeast at a hydraulic gradient of 0 005 ft/ft, which is consistent with historical flow regi no al groundwater elevation contour map was prepared by TRC using monitoring data collected on June 28, 2005 and is presented in Attachment 1 , The dissolved plume continues to be centered in the vicinity of the source area wells MW-2, MW-16, and VW-7 The extent of the hydrocarbon plume has been delineated by low or non-detectable hydrocarbon concentrations recorded in downgradient wells MW-7 and MW-15 to the southeast, cross-gradient wells MW-4 and MW-5 to the northeast and southwest, respectively, and upgradient by VW-1 to the northwest During the second quarter 2005 monitoring and sampling event, the following maximum concentrations were reported (Attachment 1) TPHg 7,400 micrograms per liter (pg/L) (VW-7) Benzene 9 0 pg/L (MW-16) MtBE 22 pg/L (MW-16) Overall, TPHg, benzene, and MtBE concentrations in groundwater continue to decline During the 2"a through the 4tr' quarters of 2004 and 1" quarter 2005, MW-11 was inaccessible due to damaged casing near the ground surface During the second quarter of 2005, TRC made repairs to MW-11 to gain access to and sample groundwater The well will be resurveyed during the third quarter CHARACTERIZATION STATUS Contamination in soil and groundwater has been adequately delineated REMEDIAL PERFORMANCE SUMMARY The ozone infection system consists of panel mounted KVA C-SpargeTM system that produces up to 4 grams of ozone per hour (0 009 pounds per hour) The system infects to 10 sparge points (SP4 through SP13) for 8 minutes cycling sixteen times a day resulting in 89 percent programmed runtime During the current quarter (March 22, 2005 y to June 22, 2005), the system was operational for 58 percent of the programmed runtime, resulting in 1,151 hours of operation and 10 pounds of ozone infection The system was down in March 2005 due to a leak in the corrugated tubing running from the compressor to the manifold The tubing was replaced on April 25, 2005 The system i has since run without problems Cumulatively, the system has operated for 14,518 hours and has infected 131 pounds of ozone into the subsurface (System data is presented in Table 1 ) The performance of the ozone infection system is evaluated by the results of monthly and quarterly groundwater sampling Monthly groundwater samples were collected from monitoring wells MW-16 and VW-7 on April 25, May 11, and June 22, 2005 The samples were analyzed for TPHg, BTEX compounds, and MtBE Results of monthly groundwater sampling events are summarized in Table 2 Concentration versus time 3 . graphs for dissolved TPHg, benzene, and MtBE in monitoring wells MW-16 and VW-7 are provided in Figures 2 and 3 3 3 6981 2Q2005 QSSR doc SECOR Intemational Incorporated R 1 J